Superelectrophilic-initiated C-H functionalization at the β-position of thiophenes: A one-pot synthesis of trans-stereospecific saddle-shaped cyclic compounds

Article abstract of DOI:10.1021/acs.joc.9b01233

Superelectrophilic-initiated direct C-H functionalization of thiophenes at the β-position was developed. A series of trans-stereospecific [2,1-a]-IF-thiophene-fused cyclic compounds (4) with saddle-shaped structure were prepared in 17-30% yields through a

Full text of DOI:10.1021/acs.joc.9b01233

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Article
Superelectrophilic-initiated C-H Functionalization at
the #-position of Thiophenes: A One-Pot Synthesis of
trans-stereospecific Saddle-shaped cyclic compounds
Ying Wei, Xiangping Zheng, Dong Qing Lin, Haoxuan Yuan, Zhipeng
Yin, Lei Yang, Yang Yu, Shasha Wang, LingHai Xie, and Wei Huang
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.9b01233 • Publication Date (Web): 31 Jul 2019
Downloaded from pubs.acs.org on July 31, 2019
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The Journal of Organic Chemistry
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Superelectrophilic-initiated C−H Functionalization at the β-position
of Thiophenes: A One-Pot Synthesis of trans-stereospecific Saddle-
shaped cyclic compounds
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Ying Wei,† Xiangping Zheng,† Dongqing Lin,† Haoxuan Yuan,† Zhipeng Yin,† Lei Yang,† Yang Yu,†
Shasha Wang,† Ling-Hai Xie,*†‡ and Wei Huang*†‡
†
Centre for Molecular Systems and Organic Devices (CMSOD), Key Laboratory for Organic Electronics and Information
Displays & Jiangsu Key Laboratory for Biosensors, Institute of Advanced Materials (IAM), National Synergistic Innovation
Center for Advanced Materials (SICAM), Nanjing University of Posts & Telecommunications, 9 Wenyuan Road, Nanjing
210023, China
‡
Shaanxi Institute of Flexible Electronics (SIFE), Northwestern Polytechnical University (NPU), 127 West Youyi Road,
Xi'an 710072, Shaanxi, China.
Supporting Information Placeholder
HO
OH
Ar/R
S
S
+
R
R
H
H
H
Superelectrophilic
HBF4 Et2O
DCE, 30 o
C
R
R
S
S
S
R
H
R
S
S
H
H
H
H
H
R = H, CH3
R = H, CH3, aryl
1.2 kcal/mol
SE: 18.0 kcal/mol
30.3 kcal/mol
trans-stereospecific saddle-shaped cyclic compounds
[
]
ABSTRACT: Superelectrophilic-initiated direct C−H functionalization of thiophenes at the β-position was developed. A series of
trans-stereospecific [2,1-a]-IF-thiophene-fused cyclic compounds (4) with saddle-shaped structure was prepared in 17%-30% yields
through a one-pot superelectrophilic Friedel–Crafts reaction of dihydroindenofluorene with thiophene derivatives. From the crystal
packing analyses of 4a, its skeleton shows both strong intermolecular π-π stacking and C-H···π stacking. Furthermore, the ring-
dependent photophysical properties of 4 were confirmed by UV-vis absorption and photoluminescence (PL) spectroscopy as well as
through the study of their fluorescence quantum yield.
Crafts reactions and other macrocyclic reactions.1 Among Th-
SPMAs, the ring closure reactions occur at the α-position of
thiophene. In contrast, reactions of the β-position are rare in the
■ INTRODUCTION
Thiophene-containing
shape-persistent
macrocycle
field of macrocyclic chemistry and only occur when the
hydrogen on the β-position is replaced by a reactive functional
group (i.e. -Br, -Li, and –B(OH)2 etc.).2,6 Current approaches
to β-position ring cyclization suffer from i) tedious synthetic
procedures, and ii) the use of dangerous solvents. Therefore,
further development of new methods that allow the facile one-
pot synthesis of highly functionalized Th-SPMAs from the
unactivated β-position of thiophene are still a challenge.
Towards this end, we demonstrate a one-pot cyclization
architectures (Th-SPMAs) have attracted significant attention
because of their potential applications in the fields of
supramolecular chemistry and materials chemistry.1 Not
surprisingly, a large number of conjugate and nonconjugate Th-
SPMAs with fascinating structures, such as cycloocta[1,2-
b:4,3-b':5,6-b'':8,7-b''']tetrathiophene,2
thiophene-fused
cycloparaphenylenes,3 calix[4]thiophenes4 and crown-
annulated oligothiophenes,5 were synthesized by metal-
catalyzed C-C coupling reactions, metalation reactions, Friedel-
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strategy to afford a type of β-position linked Th-SPMAs, which
Page 2 of 9
solvent at 30 °C (entries 1-4). CF3SO3H was an effective
superacid, and furnished a high trans-stereospecific 4a (14%)
with two H atoms at the 9-site in an opposite orientation as well
as the U-shaped product 5a (35%) and oligomeric byproducts.
The skeletal structure of 4a was further confirmed by a single-
crystal X-ray diffraction. It is worth noting that the 5a is a
product from the reaction of [2,1-a]-IFOH with the α-position
of 2,2'-bithiophene. When CH3SO3H and H2SO4 were used as
superacids, however, the yield of 4a decreased to 3%-5%. To
our delight, HBF4·Et2O afforded 4a in 27% yield. During this
process, the byproducts, including the 5a (26%) and another
undefined complex oligomer, were found. The effects of
reaction time was examined under the same conditions. As a
result, the yield of 4a decreased from 27% to 18% by increasing
the reaction time from 30 sec to 3 min. These results indicated
that the formation of oligomers may be caused by the reaction
of thiophene with the 5a and 4a. Thus, shortening of reaction
time can protect 4a from being attacked by another molecule of
[2,1-a]-IFOH. Furthermore, solution concentration was
explored. The results indicated that the yield of 4a was
decreased to 20% when the solvent concentration of DCE was
decreased to 0.01 M. When the concentration of DCE increased
to 0.1 M, the yield of 4a subsequently decreased to 15%.
Finally, the amount of HBF4·Et2O (20 equiv., 40 equiv., 80
equiv.) used into the reaction (entries 9-11) was explored. As a
result, the yield of 4a improved slightly until 60 equiv. of acid,
after which the yield remained constant.
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5
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contains simple operation, short reaction time and mild
conditions. The β-position linked Th-SPMAs allow for different
functional groups easily introducing to the α-position of
thiophene for molecular modification and structural expansion
compared with α-position linked Th-SPMAs. Moreover, due to
the ease of functionalization, such β-position linked Th-SPMAs
have been shown to exhibit superior properties in optical and
electrochemical applications.7
Our partiular interest is superelectrophilic chemistry, which
was proposed in the 1970s by Olah and coworkers8 and has
been extensively used in various organic reactions, such as the
Friedel–Crafts reaction,9 Diels−Alder reaction10 as well as other
cyclization reactions.11 Superelectrophilic chemistry is well-
known for its ability to generate di- and tri-cationic
superelectrophiles in superacidic media that exhibit
exceptionally high electrophilic reactivities.12 Compared with
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mono-cationic
electrophiles,
multiple
cationic
superelectrophiles as highly reactive electrophilic species are
capable of reacting with very weak nucleophiles (i.e.,
deactivated arenes and alkanes).
Inspired by superelectrophilic chemistry, we anticipated that
the intramolecular electrophilic cyclization of
nucleophile, such as the 3,3’-position of 2,2'-bithiophene, and a
11,12-dihydroindeno[2,1-a]fluorene ([2,1-a]-IF)-based
superelectrophilic intermediate could produce [2,1-a]-IF-
thiophene-fused cyclic compounds. [2,1-a]-IF-based
a weak
superelectrophilic intermediates can be afforded via 11,12-
dihydroindeno[2,1-a]fluorene-11,12-diol ([2,1-a]-IFOH) in the
presence of a superacid (Scheme 1). Herein, a C-C bond
formation at the β-position of thiophene has been developed via
the superacid promoted superelectrophilic Friedel–Crafts
reaction of [2,1-a]-IFOH with 2,2'-bithiophene. This
methodology provides a strategically novel access to [2,1-a]-
IF-thiophene-fused cyclic compounds with a saddle-shaped
structure (4). Their structures were analyzed by nuclear
magnetic resonance (NMR) spectroscopy and high-resolution
mass spectrometry (HRMS). Furthermore, the structure of 4a
was verified by a single-crystal X-ray diffraction. The crystal
packing of 4a shows both strong intermolecular π-π stacking
and C-H···π stacking. In addition, the ring-dependent properties
of [2,1-a]-IFOH, 4 and U-shaped product 5 were confirmed by
absorption and emission peaks and the fluorescence quantum
yield.
Table 1. Optimization of the reaction conditionsa
S
S
S
S
OH HO
S
S
S
S
Superacid
DCE
H
H
+
H
H
+
30 o
C
[2,1-a]-IFOH
4a
5a
Entry
Superacid
(eq)
CF3SO3H
(60)
CH3SO3H
(60)
H2SO4
(60)
HBF4·Et2O
(60)
HBF4·Et2O
(60)
HBF4·Et2O
(60)
HBF4·Et2O
(60)
DCE Time 4aYieldb 5aYieldb
(M)
0.05
(%)
14
(%)
35
30 s
30 s
30 s
30 s
60 s
1
2
3
4
5
6
7
8
9
10
0.05
0.05
0.05
0.05
3
40
30
26
25
22
28
32
27
26
5
Scheme 1. Superacid promoted superelectrophilic Friedel–
Crafts reaction.
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15
23
25
S
S
S
S
HO
OH
H
H
super-acid
0.05 180 s
Superelectrophilic
[2,1-a]-IFOH
4a
0.01
0.1
30 s
30 s
30 s
30 s
■ RESULTS AND DISCUSSION
HBF4·Et2O
(60)
HBF4·Et2O
(20)
HBF4·Et2O
(40)
To optimize the reaction conditions and meet the requirements
for the formation of a superelectrophile, such as excess
superacid media and high concentration,11d [2,1-a]-IFOH
(mixed stereoisomers) and, 2,2'-bithiophene were selected as
model reagents(Table 1). First, several superacids (60 equiv)
were investigated in 1,2-dichloroethane (DCE, 0.05 M) as the
0.05
0.05
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27 26
0.05
30 s
in 28%, 30% and 29% yields, respectively. However, 5,5'-
dibromo-2,2'-bithiophene showed poor reactivity, as 4h was
obtained in only 20% yield. These results indicated that
electron-donating groups facilitate the cyclization. Finally, to
study the distance-effect between two cationic groups on the
11
HBF4·Et2O
(80)
1
2
3
4
5
6
7
8
9
aReactions were carried out with [2,1-a]-IFOH (0.17 mmol),
2,2'-bithiophene (0.17 mmol), superacid in DCE. bIsolated
yield.
cyclizing reaction, [2,1-b]-IFOH as
a superelectrophile
Scheme 2. Substrate Scope of the Reactiona
precursor was subjected to the reaction sequence. However, the
expected 4k and 4l were not observed. Instead, U-shaped
byproducts 5c and 5d (Supporting Information) were achieved
in 21% and 23% yield from the reaction between the α-positions
of 2,2'-bithiophene and 2,2':5',2''-terthiophene with [2,1-b]-
IFOH, respectively, indicating an increased distance between
cationic groups in [2,1-b]-IFOH to avoid the generation of a
superelectrophile.
S
S
S
S
S
S
R
R
H
H
H
H
H
H
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R = H, 4b (trace)
R = CH3, 4c (20%)
4a (27%)
4d (20%)
S
S
(a)
S
S
S
S
S
H
H
H H
4g (28%)
4e (0%)
4f (17%)
R
R
Br
Br
S
S
S
S
S
S
S
H
H
H
H
(b)
(c)
4k (0%)
4l (0%)
R = H, 4i (30%)
=C4H9, 4j (29%)
4h (20%)
R
aReactions were carried out by using dihydroindenofluorenes
(0.17 mmol) with thiophene derivatives (0.17 mmol),
HBF4·Et2O in 0.05 M DCE.
Having established the optimal reaction conditions, we
explored the substrate scope of dihydroindenofluorenes and
thiophene derivatives in the presence of HBF4·Et2O (Scheme
2). First, to explore the influence of the thiophene chain length
of on the cyclization reaction, mono-, di-, tri-thiophenes were
explored. The results showed that when thiophene was
examined, only a trace amount of 4b was obtained, and the U-
shaped byproduct (5b, 30%)13 was obtained via the reaction of
the α-position of thiophene with [2,1-a]-IFOH. Fortunately,
when the α-position of thiophene was replaced with a methyl,
under the same conditions, 4c was obtained in 20% yield.
2,2':5',2''-terthiophene was transformed into 4d in 20% yield,
whereas the expected 4e was not observed, due to the strain
energy of 4e, 57.3 kcal·mol−1, which was larger than that of 4d
(Table S1).14 To verify the reduced reaction site of the tri-
thiophene, it was necessary to synthesize an [2,1-a]-IF-
thiophene-fused rings with a large strain energy. 1,3-
di(thiophen-2-yl)benzene was used for this reaction, and the
corresponding 4f was obtained in 17% yield. Subsequently, by
replacing both the electron-withdrawing and electron-donating
groups15 at the 5,5'-positions of the 2,2'-bithiophene with
methyl, Br, phenyl, or butylphenyl, the corresponding
cyclization products were produced smoothly. The 5,5'-
positions of 2,2'-bithiophene containing a methyl, phenyl, or
butylphenyl substituent, gave the corresponding 4g, 4i, and 4j
Figure 1. (a) 1H NMR spectra of the 5a and 4a (400 MHz, 30
°C, in CDCl3). (b) ORTEP drawing of 4a at 50% probability.
(c) Packing structure of 4a.
The conversion of [2,1-a]-IFOH to [2,1-a]-IF-thiophene-fused
cyclic compounds was confirmed by 1H and 13C NMR
spectroscopy as well as high-resolution mass spectrometry
(HRMS). Figure. 1a shows the 1H NMR spectra of the U-shaped
5a and 4a in CDCl3. The 1H NMR spectra of the U-shaped 5a,
shows four doublets at 6.80-6.81 ppm (J = 3.6 Hz), 7.00-7.01
ppm (J = 3.6 Hz), 7.04-7.05 ppm (J = 3.6 Hz) and 7.13-7.14
ppm (J = 5.2 Hz). Each doublet integrated as two hydrogens
and were assigned to protons b’, c, c’ and a of the dithiophene
group. The one triplet at 6.92-6.94 ppm (J = 3.6 Hz),
correspond to two hydrogens and was assigned to proton b of
the dithiophene group a. In comparison, the proton c and c’ of
dithiophene group peak at 7.00-7.01 ppm and 7.04-7.05 ppm
disappeared in the 1H NMR spectrum of 4a, which
demonstrated the formation of a C-C bond in the β-position of
dithiophene. Additionally, in the 1H NMR spectrum of 4a, due
to the influence of the cyclic skeleton, proton 5 on the
indenofluorene group was shielded by the induced field of the
aromatic ring current and the protons a on dithiophene as well
as protons 1, 2, 3 and 4 on indenofluorene group were
deshielded by the induced field of the aromatic ring current. The
β-proton (proton b) and α-proton (proton a) of the dithiophene
group appeared as two doublets at 6.80-6.81 ppm (J = 5.2 Hz)
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and 7.34-7.35 ppm (J = 5.2 Hz), respectively, integrating to two
Page 4 of 9
step. Then, intermediate A reacts with β-position of 2,2'-
bithiophene to obtained intermediate B by releasing one proton,
follow by intermediate B removed a molecule of water to give
complex II and finally a intramolecular electrophilic cyclization
to get 4a (II→III→4a).
1
2
3
4
5
6
7
8
hydrogens each. Protons 1, 2, 3, 4 and 5 of the indenofluorene
group appeared as a doublet at 7.58-7.59 ppm (J = 7.6 Hz), a
triplet at 7.34-7.38 ppm (J = 8.0 Hz), a triplet at 7.42-7.46 ppm
(J = 7.6 Hz), a doublet at 7.84-7.86 ppm (J = 7.6 Hz) and a
singlet at 7.83 ppm. These protons integrated as a total of ten
hydrogens. Proton c and c’ of the dithiophene group peak
disappeared in the 1H NMR spectrum of 4a due to the formation
of the cyclic ring.
To study the effect of ring size on [2,1-a]-IF-thiophene-fused
cyclic compounds, the stability and photophysical properties of
4a, 4c and 4f were carried out by density functional theory
(DFT) calculations, UV-vis absorption spectroscopy and
photoluminescence (PL) spectroscopy. A strain energy was
calculated by DFT calculations at the RB3LYP/6-31G(d) level
of theory.14 As a result, 4c and 4f have a high strain energy (SE:
18.0 kcal·mol-1 and 24.0 kcal·mol-1, respectively). In
comparison, the strain energy (SE) of 4a was 1.2 kcal·mol-1, and
it exhibited an increased stability and facile synthesis. The
photophysical properties of 4a, 4c, 4f, 5a and [2,1-a]-IFOH
were next investigated by UV-vis absorption spectroscopy and
photoluminescence (PL) spectroscopy. As shown in Figure 2
and Table 2, 4a, 4c and 4f exhibit almost the same UV-vis and
PL spectra, and their PL spectra are significantly blue-shifted in
comparison to that of [2,1-a]-IFOH and 5a. In addition, band-
gap energy (Eg) were gained from the onset edge of the UV-vis
absorption spectra. 4a, 4c and 4f were found to
The skeletal structure of 4a was not totally planar, but
saddle-shaped (Figure 1b). The dihedral angles of the
indenofluorene and the bithiophene are 56.59° and 54.86°,
respectively, and the two torsional thiophenes have an angle of
60.91° (Figure S2). The packed structure of 4a is illustrated in
Figure 1c. Such saddle-shaped backbones exhibit an
outstanding conjugated character and form torsional octatomic
rings to facilitate intermolecular π-π stacking in the presence of
indenofluorene planes. The distance between the two stacking
surfaces was approximately 3.60 Å. Furthermore, the α-position
of the thiophene and indenofluorene plane detected edge-to-
face stacking and the distance between the adjacent interlayers
was approximately 2.76 Å. Intermolecular S−S interactions
were not observed. Most importantly, the style of packing mode
allowed for a transverse longitudinal extension to from the 2-
dimensional supramolecular framework.
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58
59
60
Scheme 3. Possible mechanism for the formation of [2,1-a]-
IF-thiophene-fused cyclic compounds (4).
S
S
S
S
-H
I
.
e
t
O
u
2
t
o
E
R
F 4
O
OH
HO
H 2
B
I
III
II
H
2
-
-H
- H2
O
-
H
H
B
2 O
F
[2,1-a]-IFOH
R
.
4
o
E
u
t
t
e
2 O
HO
I
I
S
S
-H
4a
A
B
On the basis of the results described above as well as previous
studies, a possible mechanism Route I for the intramolecular
electrophilic cyclization of [2,1-a]-IFOH and the unactivated
β-position of thiophene was proposed, as depicted in Scheme 3.
First, in the presence of HBF4·Et2O, [2,1-a]-IFOH lost two
molecules of water to form the di-cationic superelectrophile I as
a highly electrophilic species.16 Then, superelectrophile I reacts
with β-position of 2,2'-bithiophene to provide complex II by
removing one proton. It is worth noting that 2,2'-bithiophene
would twisted from the coplanar anti and syn configuration to
keep the lowest energy conformers,17 and only syn
configurations could followed by a intramolecular electrophilic
cyclization to give the intermediate III. Finally, intermediate III
lost one proton to generate the trans-stereospecific 4a. Another
anti 2,2'-bithiophene in complex II tend to form oligomers due
to the active sites of thiophene far from sp3-carbon atoms of
[2,1-a]-IFOH. In the meanwhile, another potential mechanism
Route II may also exist at the same time. Different from
superelectrophile I, monocation intermediate A was generated
from [2,1-a]-IFOH by lost one H2O when acid added in the first
Figure 2. UV-vis absorption spectra (a) and PL spectra (b) of
[2,1-a]-IFOH, 4a, 4c, 4f and 5a in 10-5 M CH2Cl2.
Table 2. The stability and photophysical properties of [2,1-
a]-IFOH, 4a, 4c, 4f and 5a.
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General information. Unless otherwise information noted, all
Entry
λabs
(nm)
λem
Eg
SE
Φ
(nm) (eV) (kcal·mol-1) (%)
1
2
3
4
5
6
7
8
the solvents and reagents were purchased from commercial
suppliers and used without further purification. Some products
were purified via column chromatography over silica gel (200-
300 mesh) (from Nanjing Wanqing Chemical Instruments
Company), some were isolated by using recycling GPC (Japan
Analytical Industry Co., Ltd.) and a little of them were purified
[2,1-a]- 303,
IFOH
3.58
3.69
3.67
3.68
3.48
-
2
366
316,333
334,
348
290,
310, 326
1.2
18.0
24.0
-
29
47
52
5
4a
1
288,
310, 325
by recrystallization. H NMR and 13C{1H} NMR spectra were
350
4c
4f
recorded at 20 oC on a Varian 400 MHz and 100 MHz,
respectively. Chemical shifts are exhibited as δ in units of parts
per million (ppm) relative to internal standard (1H NMR: TMS
= 0.00 ppm) or relative residual peaks (1H NMR: 7.26 for
CDCl3, 2.50 for d6–DMSO; 13C NMR: 77.0 triplet for CDCl3,
39.25 for d6–DMSO). Multiplicities in briefly were shown as:
s (singlet); d (doublet); t (triplet); dd (doublet of doublets); m
(multiplet). High resolution (HR) mass spectrometry (MS)
experiments were performed on Thermo Fisher Scientific LTQ
FTICR-MS and Waters Micromass GCT. Coupling constants
are reported as a J value in Hz.
334,
348
290,
311, 327
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379
5a
314, 330
be 3.69 eV, 3.67 eV and 3.68 eV, higher than that of [2,1-a]-
IFOH (3.58 eV) and 5a (3.48 ev), respectively. Most notably,
the fluorescence quantum yield values of [2,1-a]-IFOH and U
shaped product 5a were quite low in CH2Cl2. However, the
rings have a significant progress and the fluorescence quantum
yield of 4a, 4c and 4f were 29%, 47% and 52% in CH2Cl2,
respectively. The results indicate that the ring skeleton has an
influence on the indenofluorenol electronic structure. The ring
strain of [2,1-a]-IF-thiophene-fused cyclic compounds,
however, has almost no effect on the absorption and emission
spectra.
Preparation of indeno[2,1-a]fluorene-11,12-dione. The
synthesis of the indeno[2,1-a]fluorene-11,12-dione,18
including intermediates Dimethyl 1',4'-dihydro-[1,1':4',1''-
terphenyl]-2',3'-dicarboxylate (1),19 Dimethyl [1,1':4',1''-
terphenyl]-2',3'-dicarboxylate (2),20 have been previously
reported.
Dimethyl
1',4'-dihydro-[1,1':4',1''-terphenyl]-2',3'-
dicarboxylate (1). White solid. 88% yield. 1H NMR (400 MHz,
CDCl3) δ: 7.38-7.34 (m, 4H), 7.31-7.28 (m, 6H), 5.81 (s, 2H),
4.50 (s, 2H), 3.58 (s, 6H). 13C{1H} NMR (100 MHz, CDCl3) δ:
167.9, 141.2, 135.7, 128.8, 128.3, 127.2, 126.1, 52.1, 44.0.
Dimethyl [1,1':4',1''-terphenyl]-2',3'-dicarboxylate (2).
White solid. 91% yield.. 1H NMR (400 MHz, CDCl3) δ: 7.52 (s,
2H), 7.45-7.41 (m, 4H), 7.40-7.38 (m, 4H), 7.37-7.36 (t, J = 3.2
Hz, 2H), 3.61 (s, 6H). 13C{1H} NMR (100 MHz, CDCl3) δ:
168.9, 139.9, 139.7, 132.1, 131.7, 128.4, 128.3, 127.8, 52.4.
Indeno[2,1-a]fluorene-11,12-dione. Yellow solid. Yield:
95%. 1H NMR (400 MHz, CDCl3) δ: 7.70-7.69 (d, J = 7.2 Hz,
2H), 7.60 (s, 2H), 7.50-7.49 (d, J = 4 Hz, 4H), 7.33-7.30 (m,
2H). 13C{1H} NMR (100 MHz, CDCl3) δ: 145.2, 143.6, 134.7,
133.7, 132.4, 129.5, 124.8, 120.1.
■ CONCLUSIONS
In summary, we have developed a novel superelectrophilic
Friedel–Crafts reaction between dihydroindenofluorene and
thiophene derivatives for the one-pot construction of [2,1-a]-
IF-thiophene-fused cyclic compounds with a saddle-shaped
structure in 17%-30% yields under mild conditions. The
structure of 4a was linked by the β-position of 2,2'-bithiophene
and sp3-carbon atoms of [2,1-a]-IFOH to form a saddle-shaped
compound which was verified by a single-crystal X-ray
diffraction, and its crystal packing show both strong
intermolecular π-π stacking and edge-to-face stacking. In
addition, due to the existence of active sites on 2,2'-bithiophene
and dihydroindenofluorene, respectively, further molecular
modification and structural expansion can be performed on 4a.
To study the effect of ring skeleton on [2,1-a]-IF-thiophene-
fused cyclic compounds, the photophysical properties of 4a, 4c,
4f, 5a and [2,1-a]-IFOH were investigated. The results show
that 4a, 4c and 4f exhibit almost the similar UV-vis and PL
spectra with λabs at near 310, 325 nm and λem at near 350 nm.
Moreover, compared to 5a and [2,1-a]-IFOH, [2,1-a]-IF-
thiophene-fused cyclic compounds 4a, 4c and 4f have a
significant progress in the fluorescence quantum yield which
indicating the ring skeleton has an influence on the
indenofluorenol electronic structure. Further work on
applications of [2,1-a]-IF-thiophene-fused cyclic compounds
type compounds is ongoing in our laboratory.
Synthesis of [2,1-a]-IFOH. Indeno[2,1-a]fluorene-11,12-
dione (1 g, 3.54 mmol) was dissolved in methyl alcohol (100
mL). The reaction mixture was stirred at room tempreture, and
small portions (ca 20 mg) of sodium borohydride (total: 200 mg,
5.3 mmol) were added to the solution every two minutes. The
excess of sodium borohydride was reduced by addition of water
(100 mL) and then left standing the solution until the precipitate
completely precipitated. The yellow precipitate formed was
further collected by filtration, washed with water and dried in
an oven at 50°C to give [2,1-a]-IFOH as a colourless solid (0.91
g, 3.2 mmol).
Yellow solid (0.91 g, 90% yield); 1H NMR (400 MHz, DMSO-
d6) δ: 7.83-7.81 (d, J = 9.6 Hz, 4H), 7.63-7.61 (d, J = 6.8 Hz,
2H), 7.44-7.40 (t, J = 7.2 Hz, 2H), 7.36-7.32 (t, J = 7.2 Hz, 2H),
6.14 (s, 2H), 5.92 (s, 2H). 13C{1H} NMR (100 MHz, DMSO-
d6) δ: 145.9, 143.7, 140.3, 139.7, 129.2, 128.1, 125.7, 121.1,
+
120.7, 73.6. HRMS (EI-TOF) m/z: [M]+ calcd for C20H14O2 ,
286.0994; found, 286.1001.
Preparation of Indeno[2,1-b]fluorene-10,12-dione. The
synthesis of the Indeno[2,1-b]fluorene-10,12-dione,18
including intermediates 4,6-Dibromoisophthalic acid (3a),
Diethyl 4,6-dibromoisophthalate (3b), Diethyl [1,1':3',1''-
■ EXPERIMENTAL SECTION
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Page 6 of 9
terphenyl]-4',6'-dicarboxylate (3c) have been previously
reported.
Synthesis of 5,5'-Bis(4-butylphenyl)-2,2'-bithiophene. The
5,5'-bis(4-butylphenyl)-2,2'-bithiophene was synthesized as the
same way of 5,5'-diphenyl-2,2'-bithiophene and purified by
column chromatography (silica gel, pure petroleum ether) to
give 5,5'-bis(4-butylphenyl)-2,2'-bithiophene (1.7 g, 4.0 mmol).
Yellow solid (1.7 g, 85% yield) 1H NMR (400 MHz, CDCl3) δ:
7.53-7.51 (d, J = 8.0 Hz, 4H), 7.21-7.19 (m, 6H), 7.15-7.14 (d,
J = 3.6 Hz, 2H), 2.65-2.61 (t, J = 7.6 Hz, 4H), 1.64-1.60 (t, J =
8.0 Hz, 4H), 0.96-0.93 (t, J = 7.2 Hz, 4H). 13C{1H} NMR (100
MHz, CDCl3) δ: 143.2, 142.6, 136.3, 131.5, 129.0, 125.5, 124.3,
123.3, 35.4, 33.6, 22.4, 14.0. HRMS (ESI-TOF) m/z: [M+H]+
calcd for C28H31S2+ , 431.1862; found, 431.1859.
1
2
3
4
5
6
7
8
4,6-Dibromoisophthalic acid (3a). White solid. Yield: 65%.
1H NMR (400 MHz, DMSO-d6) δ: 8.15 (s, 1H), 8.12 (s, 1H),
2.27 (s, 2H). 13C{1H} NMR (100 MHz, DMSO-d6) δ: 166.4,
138.9, 134.6, 133.6, 133.1, 132.8, 124.2, 100.0.
Diethyl 4,6-dibromoisophthalate (3b). White solid. Yield:
40%. 1H NMR (400 MHz, DMSO-d6) δ: 8.18 (s, 1H), 8.10 (s,
1H), 4.37-4.31 (m, 4H), 1.34-1.31 (t, J = 7.2 Hz, 6H). 13C{1H}
NMR (100 MHz, DMSO-d6) δ: 164.7, 139.1, 132.8, 132.2,
124.7, 62.5, 14.4.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Diethyl
[1,1':3',1''-terphenyl]-4',6'-dicarboxylate
(3c).
1
Colorless oil. Yield: 90%. H NMR (400 MHz, DMSO-d6) δ:
8.10 (s, 1H), 7.42-7.35 (m, 11H), 4.10-4.04 (m, 4H), 0.98-0.95
(t, J = 7.2 Hz, 6H). 13C{1H} NMR (100 MHz, DMSO-d6) δ:
167.5, 144.5, 139.9, 133.1, 131.0, 130.4, 129.4, 128.7, 128.3,
127.9, 127.1, 61.5, 13.9.
Synthesis
of
1,3-Di(thiophen-2-yl)benzene.
1,3-
dibromobenzene (3 g, 12.8 mmol), thiophen-2-ylboronic acid
(5 g, 38.5 mmol), tetrakis(triphenylphosphine) palladium0 (1.3
g, 1.1 mmol) and potassium carbonate (5 g, 63.7 mmol) were
dissolved in a mixture THF/water (2.5:1, 150 mL) under an
nitrogen atmosphere. The resulting mixture was stirred
overnight at 70°C in an oil bath. The mixed organic phase was
washed with water, extracted with CH2Cl2, dried over
anhydrous MgSO4 before organic phase was filtered and
concentrated under low pressure. The crude product was
purified by column chromatography (silica gel, pure petroleum
ether) to give 1,3-di(thiophen-2-yl)benzene (2.6 g, 10.6 mmol).
White solid (2.6 g, 83% yield) 1H NMR (400 MHz, CDCl3) δ:
7.85 (s, 1H), 7.55-7.53 (dd, J = 7.6 , 1.2 Hz, 2H), 7.42-7.40 (d,
J = 7.6 Hz, 1H), 7.38-7.37 (dd, J = 3.6 , 1.2 Hz, 2H), 7.33-7.31
(dd, J = 5.0, 1.0 Hz, 2H), 7.13-7.11 (dd, J = 5.2, 3.6 Hz, 2H).
13C{1H} NMR (100 MHz, CDCl3) δ: 144.0, 135.1, 129.5, 128.1,
125.1, 123.6, 123.5. HRMS (ESI-TOF) m/z: [M+H]+ calcd for
C14H11S2+ , 243.0297; found, 243.0296.
General procedure for synthesis of compounds 4 and 5 (4a
is an example). In a round-bottom flask charged with [2,1-a]-
IFOH (50.0 mg, 0.17mmol) and 2,2'-bithiophene(29.0 mg,
0.17mmol) in 3.4 mL (0.05 M) 1, 2-dichloroethane (DCE), then
60 equiv HBF4•Et2O was added into the mixture and stirred for
30s at 30 oC in an oil bath. Subsequently, H2O was added，and
the mixture was extracted with CH2Cl2. The mixed organic
phase was washed with potassium carbonate solution, dried
over anhydrous MgSO4 before organic phase was filtered and
concentrated under low pressure. The crude product was
purified by recycling GPC to give 4a in 27% yield.
Indeno[2,1-b]fluorene-10,12-dione. Brown solid. Yield:
90%. 1H NMR (400 MHz, CDCl3) δ: 7.89 (s, 1H), 7.69-7.67 (d,
J = 7.2 Hz, 2H), 7.65 (s, 1H), 7.61-7.59 (d, J = 7.2 Hz, 2H),
7.56-7.52 (t, J = 7.2 Hz, 2H), 7.40-7.36 (t, J = 7.2 Hz, 2H).
13C{1H} NMR (100 MHz, CDCl3) δ: 151.5, 142.8, 134.9, 134.8,
134.6, 130.5, 124.5, 121.1, 120.1.
Synthesis of [2,1-b]-IFOH. The title compound was
synthesized as the same way of [2,1-a]-IFOH. The NMR
spectrum data could not be measured due to the extremely poor
solubility of the product. Brown solid (0.90 g, 89% yield);
+
HRMS (EI-TOF) m/z: [M]+ calcd for C20H14O2 , 286.0094;
found, 286.1000.
Synthesis of 5,5'-Dibromo-2,2'-bithiophene. To a solution
of 2,2'-bithiophene (3 g, 18.0 mmol) in acetone (30 ml) were
added N-bromosuccinimide (9.7 g, 54.1 mmol) by dropping in
a solution of acetone (30 ml). Then the mixture was stirred at
the room temperature until the dripped off. After that,
o
increasing the reaction temperature to 60 C in an oil bath
overnight. The mixed organic phase was washed with water,
extracted with CH2Cl2, dried over anhydrous MgSO4 before
organic phase was filtered and concentrated under low pressure.
The crude product was purified by column chromatography
(silica gel, pure petroleum ether) to give 5,5'-dibromo-2,2'-
bithiophene (5.8 g, 16.2 mmol).
Yellow solid (5.8 g, 90% yield);1H NMR (400 MHz, CDCl3) δ:
6.96-6.95 (d, J = 3.6 Hz, 2H), 7.85-7.84 (d, J = 4 Hz, 2H).
13C{1H} NMR (100 MHz, CDCl3) δ: 137.8, 130.7, 124.2, 111.6.
[2,1-a]-IF-thiophene-fused cyclic compound (4a). White solid
(19.6 mg, 27% yield); 1H NMR (400 MHz, CDCl3) δ: 7.86-7.83
(m, 4H), 7.59-7.57 (d, J = 8 Hz, 2H), 7.46-7.42 (t, J = 7.2 Hz,
2H), 7.37-7.34 (m, 4H), 6.81-6.80 (d, J = 5.2 Hz, 2H), 4.95 (s,
2H). 13C{1H} NMR (100 MHz, CDCl3) δ: 145.3, 141.7, 140.3,
139.3, 131.5, 127.5, 126.9, 126.8, 125.6, 120.2, 119.3, 47.0.
+
HRMS (ESI-TOF) m/z: [M]+ calcd for C8H4Br2S2 , 321.8116;
found, 321.8113.
Synthesis of 5,5'-Diphenyl-2,2'-bithiophene. 5,5'-dibromo-
2,2'-bithiophene (4 g, 12.4 mmol), phenylboronic acid (3.8 g,
31.1 mmol), tetrakis-(triphenylphosphine) palladium0 (1.4 g,
1.2 mmol) and potassium carbonate (5 g, 36.2 mmol) were
dissolved in a mixture THF/water (2.5:1, 150 mL) under an
nitrogen atmosphere. The resulting mixture was stirred
overnight at 70°C in an oil bath. The mixed organic phase was
washed with water, extracted with CH2Cl2, dried over
anhydrous MgSO4 before organic phase was filtered and
concentrated under low pressure. The crude product was
purified by column chromatography (silica gel, pure petroleum
ether) to give 5,5'-diphenyl-2,2'-bithiophene (3.2 g, 10.0 mmol).
+
HRMS (EI-TOF) m/z: [M]+ calcd for C28H16S2 , 416.0693;
found, 416.0695.
[2,1-a]-IF-thiophene-fused cyclic compound (4c). Brown
1
solid (12.7 mg, 20% yield); H NMR (400 MHz, CDCl3) δ:
8.07-8.05 (d, J = 7.6 Hz, 2H), 7.84-7.82 (d, J = 7.6 Hz, 2H),
7.69 (s, 2H), 7.44-7.40 (t, J = 7.6 Hz, 2H), 7.35-7.32 (t, J = 6.4
Hz, 2H), 5.05 (s, 2H), 2.48 (s, 6H). 13C{1H} NMR (100 MHz,
CDCl3) δ: 144.3, 143.8, 143.7, 138.4, 136.7, 130.1, 127.6, 127.4,
125.7, 121.0, 119.4, 47.6, 29.7, 16.1. HRMS (ESI-TOF) m/z:
[M+H]+ calcd for C26H19S+, 363.1202; found, 363.1200.
1
Yellow solid (3.2 g, 81% yield) H NMR (400 MHz, CDCl3)
[2,1-a]-IF-thiophene-fused cyclic compound (4d). Brown
1
7.62-7.61 (d, J = 6.4 Hz, 4H), 7.41-7.37 (t, J = 7.6 Hz, 4H),
7.31-7.25 (m, 6H), 7.18 (s, 2H). 13C{1H} NMR (100 MHz,
CDCl3) δ: 129.0, 127.6, 125.6, 124.5, 123.8. HRMS (ESI-TOF)
solid (17.4 mg, 20% yield); H NMR (400 MHz, CDCl3) δ:
7.88-7.84 (m, 4H), 7.63-7.58 (m, 2H), 7.48-7.43 (m, 2H), 7.40-
7.35 (m, 2H), 7.19-7.18 (dd, J = 5.0, 1.0 Hz, 1H), 7.15-7.14 (dd,
J = 3.6, 1.2 Hz, 1H), 7.00-6.97 (m, 2H), 6.87 (s, 1H), 6.82-6.81
+
m/z: [M+H]+ calcd for C20H15S2 : 319.0610; found, 319.0607.
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The Journal of Organic Chemistry
(d, J = 5.2 Hz, 1H), 5.05 (s, 1H), 4.93 (s, 1H). 13C{1H} NMR
(100 MHz, CDCl3) δ: 145.2, 145.0, 141.7, 140.3, 140.0, 139.6,
139.3, 138.5, 137.1, 131.1, 130.2, 127.8, 127.6, 127.1, 127.0,
126.8, 125.6, 124.8, 123.9, 123.4, 120.2, 119.4. HRMS (ESI-
136.5, 127.7, 127.5, 126.9, 125.1, 124.0, 123.3, 123.0, 120.1,
+
48.0. HRMS (EI-TOF) m/z: [M]+ calcd for C36H22S4 , 582.0609;
1
2
3
4
5
6
7
8
found, 582.0604.
11,12-Di(thiophen-2-yl)-11,12-dihydroindeno[2,1-a]fluorene
(5b). Yellow solid (17.5 mg, 30% yield); 1H NMR (400 MHz,
CDCl3) δ: 7.91 (s, 2H), 7.82-7.80 (d, J = 7.2 Hz, 2H), 7.38-7.34
(t, J = 7.2 Hz, 2H), 7.33-7.32 (d, J = 7.6 Hz, 2H), 7.25-7.21 (t,
J = 7.2 Hz, 2H), 7.15-7.14 (d, J = 5.2 Hz, 2H), 6.95-6.93 (dd,
J = 5.2, 3.6 Hz, 2H), 6.78-6.77 (d, J = 3.2 Hz, 2H), 5.06 (s, 2H).
13C{1H} NMR (100 MHz, CDCl3) δ: 165.6, 165.5, 147.5, 143.0,
142.8, 140.8, 140.0, 129.8, 129.7, 129.6, 127.5, 127.3, 126.5,
125.9, 125.0, 124.4, 120.0, 119.9, 63.0, 47.8. HRMS (ESI-TOF)
+
TOF) m/z: [M+H]+ calcd for C32H19S3 , 499.0643; found,
499.0639.
[2,1-a]-IF-thiophene-fused cyclic compound (4f). White solid
(14.6 mg, 17% yield); 1H NMR (400 MHz, CDCl3) δ: 7.91 (s,
1H), 7.88-7.83 (m, 2H), 7.82 (s, 2H), 7.61-7.59 (d, J = 7.2 Hz,
1H), 7.56-7.53 (dd, J = 8.0, 2.0 Hz, 1H), 7.51-7.49 (d, J = 7.6
Hz, 2H), 7.47-7.42 (m, 2H), 7.37-7.34 (m, 3H), 7.31-7.29 (m,
2H), 7.10-7.08 (m, 2H), 6.74-6.73 (d, J = 5.2 Hz, 1H), 5.05 (s,
1H), 4.90 (s, 1H). 13C{1H} NMR (100 MHz, CDCl3) δ: 145.4,
145.2, 143.6, 142.3, 141.9, 141.5, 14.9, 139.3, 139.0, 138.5,
138.2, 137.0, 135.6, 132.8, 128.1, 127.6, 127.5, 127.0, 126.9,
126.8, 126.2, 126.1, 125.5, 125.2, 125.0, 123.5, 120.2, 119.3,
119.2, 50.0, 46.5. HRMS (ESI-TOF) m/z: [M+H]+ calcd for
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
+
m/z: [M+H]+ calcd for C28H19S2 , 419.0923; found, 419.0919.
10,12-di([2,2'-bithiophen]-5-yl)-10,12-dihydroindeno[2,1-
b]fluorene(5c). Yellow solid (15.3 mg, 21% yield); Due to the
presence of isomers and difficulty in separation, there is a bias
in the NMR spectrum. 1H NMR (400 MHz, CDCl3) δ: 8.19-8.17
(m, 1H), 7.91-7.89 (d, J = 7.6 Hz, 3H), 7.58 (s, 1H), 7.50-7.48
(m, 3H), 7.46-7.44 (m, 3H), 7.35-7.31 (d, J = 7.2 Hz, 3H), 7.15-
7.14 (d, J = 4.8 Hz, 2H), 7.05-7.04 (d, J = 3.6 Hz, 2H), 7.03-
7.02 (d, J = 3.6 Hz, 2H), 6.97-6.96 (d, J = 3.6 Hz, 2H), 6.95-
6.93 (m, 2H), 5.31 (s, 2H). 13C{1H} NMR (100 MHz, CDCl3)
δ: 146.9, 146.5, 143.5, 140.6, 140.4, 137.5, 136.4, 127.9, 127.7,
127.5, 126.4, 126.2, 125.4, 124.1, 123.4, 123.3, 122.3, 120.1,
111.4, 49.2.
+
C34H21S2 , 493.1079; found, 493.1076.
[2,1-a]-IF-thiophene-fusedcyclic compound (4g). Red solid
(21.7 mg, 28% yield); 1H NMR (400 MHz, CDCl3) δ: 7.85-7.81
(m, 4H), 7.60-7.58 (d, J = 7.6 Hz, 2H), 7.45-7.42 (t, J = 7.2 Hz,
2H), 7.37-7.34 (t, J = 7.6 Hz, 2H), 6.44 (s, 2H), 4.94 (s, 2H),
2.42 (s, 6H). 13C{1H} NMR (100 MHz, CDCl3) δ: 145.5, 141.7,
140.9, 140.5, 139.2, 138.8, 129.3, 127.4, 126.8, 125.6, 125.0,
120.1, 119.2, 47.2, 15.6. HRMS (ESI-TOF) m/z: [M+H]+ calcd
+
for C30H21S2 , 445.1079; found, 445.1074.
10,12-di([2,2':5',2''-terthiophen]-5-yl)-10,12-dihydroindeno-
[2,1-b]fluorene(5d). Yellow solid (20.0 mg, 23% yield); Due to
the presence of isomers and difficulty in separation, there is a
bias in the NMR spectrum. 1H NMR (400 MHz, CDCl3) δ: 8.17
(s, 1H), 7.91-7.89 (d, J = 7.6 Hz, 3H), 7.58 (s, 1H), 7.50-7.48
(m, 3H), 7.46-7.44 (m, 3H), 7.36-7.32 (d, J = 7.2 Hz, 4H), 7.20-
7.18 (d, J = 4.8 Hz, 2H), 7.13-7.12 (d, J = 3.6 Hz, 2H), 7.04-
7.03 (d, J = 3.6 Hz, 2H), 7.01-7.00 (d, J = 4.0 Hz, 2H), 6.98-
6.97 (m, 2H), 6.92-6.91 (d, J = 3.6 Hz, 2H), 5.31 (s, 2H).
13C{1H} NMR (100 MHz, CDCl3) δ: 146.9, 146.5, 143.7, 140.7,
140.4, 137.2, 136.3, 136.1, 135.9, 128.0, 127.9, 127.6, 127.5,
126.5, 125.4, 124.4, 124.3, 123.9, 123.6, 123.3, 122.3, 120.1,
[2,1-a]-IF-thiophene-fused cyclic compound (4h). Brown
1
solid (20.0 mg, 20% yield); H NMR (400 MHz, CDCl3) δ:
7.86-7.83 (m, 4H), 7.58-7.56 (d, J = 7.6 Hz, 2H), 7.48-7.44 (t,
J = 7.6 Hz, 2H), 7.40-7.37 (t, J = 6.8 Hz, 2H), 6.76 (s, 2H), 4.93
(s, 2H). 13C{1H} NMR (100 MHz, CDCl3) δ: 144.7, 142.1,
140.6, 139.9, 139.4, 132.4, 131.2, 127.9, 127.2, 124.5, 120.5,
119.6, 112.6. HRMS (EI-TOF) m/z: [M]+ calcd for
+
C28H14Br2S2 , 571.8904; found, 571.8912.
[2,1-a]-IF-thiophene-fused cyclic compound (4i). Yellow
1
solid (29.8 mg, 30% yield); H NMR (400 MHz, CDCl3) δ:
7.90-7.86 (m, 4H), 7.65-7.64 (d, J = 7.6 Hz, 2H), 7.54-7.53 (d,
J = 7.2 Hz, 4H), 7.49-7.45 (t, J = 7.2 Hz, 2H), 7.40-7.38 (d, J
= 6.4 Hz, 2H), 7.36-7.32 (t, J = 7.2 Hz, 4H), 7.28-7.25 (t, J =
7.6 Hz, 2H), 7.03 (s, 2H), 5.06 (s, 2H). 13C{1H} NMR (100
MHz, CDCl3) δ: 145.5, 145.2, 141.7, 140.2, 139.3, 134.1, 130.7,
128.9, 127.8, 127.6, 127.1, 125.8, 125.7, 123.0, 120.2, 119.5,
+
49.2. HRMS (EI-TOF) m/z: [M]+ calcd for C44H26S6 , 746.0359;
found,746.0365.
■ ASSOCIATED CONTENT
Supporting Information
+
47.3. HRMS (EI-TOF) m/z: [M]+ calcd for C40H24S2 , 568.1319;
found, 568.1329.
The Supporting Information is available free of charge on the
ACS Publications website.
[2,1-a]-IF-thiophene-fused cyclic compound (4j). Yellow
1
solid (34.5 mg, 29% yield); H NMR (400 MHz, CDCl3) δ:
7.89-7.86 (m, 4H), 7.65-7.63 (d, J = 7.6 Hz, 2H), 7.50-7.46 (m,
2H), 7.45-7.42 (d, J = 8 Hz, 4H), 7.39-7.35 (t, J = 8.4 Hz, 2H),
7.16-7.14 (d, J = 8.4 Hz, 4H), 6.98 (s, 2H), 5.05 (s, 2H), 2.61-
2.57 (t, J = 7.6 Hz, 4H), 1.63-1.59 (t, J = 7.6 Hz, 4H), 1.38-
1.32(m, 4H), 0.94-0.90 (t, J = 7.2 Hz, 6H). 13C{1H} NMR (100
MHz, CDCl3) δ: 145.6, 145.3, 142.8, 141.7, 140.3, 139.3, 131.6,
130.3, 129.0, 127.6, 127.0, 125.7, 122.5, 120.2, 119.4, 47.3,
35.4, 33.5, 22.4, 14.0. HRMS (EI-TOF) m/z: [M]+ calcd for
Accession Codes
CCDC 1887120 and 1887122 contain the supplementary
crystallographic data for this paper. These data can be obtained free
of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing
data_request@ccdc.cam.ac.uk, or by contacting The Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2
1EZ, UK; fax: +44 1223 336033.
+
C48H40S2 , 680.2571; found, 680.2565.
11,12-Di([2,2'-bithiophen]-5-yl)-11,12-dihydroindeno[2,1-
1
a]fluorene (5a). Brown solid (18.9 mg, 26% yield); H NMR
AUTHOR INFORMATION
Corresponding Author
* E-mail: iamlhxie@njupt.edu.cn
* E-mail: iamwhuang@nwpu.edu.cn
(400 MHz, CDCl3) δ: 7.93 (s, 2H), 7.83-7.81 (d, J = 8.4 Hz,
2H), 7.40-7.37 (t, J = 6.4 Hz, 4H), 7.27-7.24 (t, J = 7.2 Hz, 2H),
7.15-7.13 (d, J = 5.2 Hz, 2H), 7.05-7.04 (d, J = 3.6 Hz, 2H),
7.01-7.00 (d, J = 3.6 Hz, 2H), 6.94-6.92 (dd, J = 5.2, 3.6 Hz,
2H), 6.81-6.80 (d, J = 3.6 Hz, 2H), 5.13 (s, 2H). 13C{1H} NMR
(100 MHz, CDCl3) δ: 147.2, 142.7, 142.1, 140.8, 140.0, 137.6,
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The Journal of Organic Chemistry
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A. Electrophilic reactions at single bonds. XVIII. Indication of
Notes
protosolvated de facto substituting agents in the reactions of alkanes
with acetylium and nitronium ions in superacidic media. J. Am. Chem.
Soc. 1975, 97, 2928-2929. (b) Olah, G. A. Superelectrophiles. Angew.
Chem. Int. Ed. Engl. 1993, 32, 767-788. (c) Naredla, R. R.; Klumpp,
D. A. Contemporary carbocation chemistry: applications in organic
synthesis. Chem. Rev. 2013, 113, 6905-6948.
(9) (a) Iakovenko, R. O.; Kazakova, A. N.; Muzalevskiy, V. M.;
Ivanov, A. Y.; Boyarskaya, I. A.; Chicca, A.; Petrucci, V.; Gertsch,
J.; Krasavin, M.; Starova, G. L.; Zolotarev, A. A.; Avdontceva, M. S.;
Nenajdenko, V. G.; Vasilyev, A. V. Reactions of CF 3-enones with
arenes under superelectrophilic activation: A pathway to trans-1, 3-
diaryl-1-CF3-indanes, new cannabinoid receptor ligands. Org. Biomol.
Chem. 2015, 13, 8827-8842. (b) Lin, D.-Q.; Wei, Y.; Ou, C.-J.; Huang,
H.; Xie, L.-H.; Tang, L.; Huang, W. Carbon cationic relay via
superelectrophiles: Synthesis of spiro-diazafluorenes. Org. Lett. 2016,
18, 6220-6223.
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The authors declare no competing financial interest.
ACKNOWLEDGMENT
This work was supported by National Natural Science Foundation
of China (Grant Nos. 21774061, 21602111, 91833306, 61136003,
61604081, 2150314), National Basic Research Program of China
(Grant No. 2015CB932202), Natural Science Foundation of
Jiangsu Province of China (BM2012010), Synergetic Innovation
Centre for Organic Electronics and Information Displays, Nanjing
University of Posts and Telecommunications Scientific Foundation
NUPTSF (NY217082), the Six Peak Talents Foundation of Jiangsu
Province (XCL-CXTD-009) and Postgraduate Research & Practice
Innovation Program of Jiangsu Province (SJCX18_0302,
46030CX17747)
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(10) Vuong, H.; Dash, B. P.; Lill, S. O. N.; Klumpp, D. A. Diels–Alder
reactions with ethylene and superelectrophiles. Org. Lett. 2018, 20,
1849-1852.
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relationship study of electron-deficient dihydroindeno [2, 1-b] fluorene
derivatives for n-type organic field effect transistors. J. Mater. Chem.
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